Presently, studies are underway to use RACH (Random Access Channel) for initial access from a radio communication mobile station apparatus (hereinafter simply “mobile station”) to a radio communication base station apparatus (hereinafter simply “base station”), in 3GPP RAN LTE (Long Term Evolution) (see Non-Patent Document 1). The RACH is utilized, for example, to make an association request and a resource request to the base station, and in initial access upon acquiring uplink transmission timing synchronization.
A mobile station transmitting a RACH signal selects one of a plurality of unique signatures in the RACH and transmits the selected signature to the base station to distinguish itself from other mobile stations transmitting RACH signals.
Moreover, in the RACH, taking into account that a plurality of signatures are transmitted from a plurality of mobile stations at the same time, studies are underway to use code sequences having low cross-correlation and high autocorrelation as signatures so as to demultiplex and detect those signatures in the base station. As a code sequence having such characteristics, the CAZAC (Constant Amplitude Zero Auto-Correlation) sequence is known, which is one of GCL (Generalized Chirp-Like) sequences (see Non-Patent Document 2).
Furthermore, to reduce the processing delay after the initial access, studies are underway to report, in the RACH, control information including the mobile station ID, the reason for RACH transmission, bandwidth allocation request information (QoS information, the amount of data, and so on), and downlink received quality information (see Non-Patent Document 3).    Non-patent Document 1: 3GPP TSG-RAN WG1 LTE Ad Hoc Meeting, R1-060047, NTT DoCoMo, NEC, Sharp, “Random Access Transmission in E-UTRA Uplink,” Helsinki, Finland, 23-25 Jan. 2006    Non-patent Document 2: 3GPP TSG-RAN WG1 LTE Ad Hoc Meeting, R1-060046, NTT DoCoMo, NEC, Sharp, “Orthogonal Pilot Channel Structure in E-UTRA Uplink,” Helsinki, Finland, 23-25 Jan. 2006    Non-patent Document 3: 3GPP TSG-RAN WG1 LTE Ad Hoc Meeting, R1-060480, Qualcomm, “Principles of RACH,” Denver, USA, 13-17 Feb. 2006